docs: def _get_audio_filter_cmd(self):
          """
          Return filter_complex command and output labels needed
          """
          all_filters = []
          output_labels = []
  
          for audio_stream in self.streams['audio'].values():
              if self.ffmpeg_normalize.normalization_type == 'ebu':
                  stream_filter = audio_stream.get_second_pass_opts_ebu()
              else:
                  stream_filter = audio_stream.get_second_pass_opts_peakrms()
              input_label = '[0:{}]'.format(audio_stream.stream_id)
              output_label = '[norm{}]'.format(audio_stream.stream_id)
              output_labels.append(output_label)
              all_filters.append(input_label + stream_filter + output_label)
  
          filter_complex_cmd = ';'.join(all_filters)
  
          return filter_complex_cmd, output_labels